Methodology for charging batteries safely

ABSTRACT

An apparatus and method for identifying a presence of a short circuit in a battery pack. A fault-detection apparatus for a charging system that rapidly charges a collection of interconnected lithium ion battery cells, the safety system includes a data-acquisition system for receiving a set of data parameters from the collection while the charging system is actively charging the collection; a monitoring system evaluating the set of data parameters to identify a set of anomalous conditions; and a controller comparing the set of anomalous conditions against a set of predetermined profiles indicative of an internal short in one or more cells of the collection, the controller establishing an internal-short state for the collection when the comparing has a predetermined relationship to the set of predetermined profiles.

CROSS REFERENCE TO RELATED APPLICATIONS

The present U.S. Utility patent application claims priority pursuant to35 U.S.C. §120 as a continuation of U.S. Utility application Ser. No.14/499,757, entitled “METHODOLOGY FOR CHARGING BATTERIES SAFELY”, filedSep. 29, 2014, issuing as U.S. Pat. No. 9,506,990 on Nov. 29, 2016,which is a divisional of U.S. Utility application Ser. No. 12/970,838,entitled “METHODOLOGY FOR CHARGING BATTERIES SAFELY”, filed Dec. 16,2010, now U.S. Pat. No. 8,866,444, issued on Oct. 21, 2014, which claimspriority pursuant to 35 U.S.C. §119(e) to U.S. Provisional ApplicationNo. 61/352,659, entitled “METHODOLOGY FOR CHARGING BATTERIES SAFELY”,filed Jun. 8, 2010, all of which are hereby incorporated herein byreference in their entirety and made part of the present U.S. Utilitypatent application for all purposes.

BACKGROUND OF THE INVENTION

The present invention relates generally to batteries and battery packsand, more particularly, to a method of identifying the presence of aninternal short within a cell of a battery or battery pack.

Internal-cell shorts may reduce the performance capability of, or causehazardous conditions for, a battery pack. These shorts may be caused bymanufacturing/design defects (e.g., metal-particle contamination thatpunctures the separator creating a path for electrons between the twoelectrodes or extends around an edge of the separator), poor cell design(e.g., a configuration permitting edges of the electrodes to touch, ormetal contamination in the active material that dissolves and plates toform a bridge between the electrodes), or electrochemical abuse. Shortscaused by manufacturing defects have resulted in the recall of manylithium-ion batteries and have motivated significant improvements inmanufacturing-quality control (e.g., implementation of cleanmanufacturing conditions, magnets to capture metal contamination, andthe like.). Through these improvements, the failure rate of lithium-ionbatteries to thermal events caused by internal shorts in consumerapplications has decreased to ˜1-5 ppm for the large-volumemanufacturers. Internal-cell shorts may also be caused by battery aging(e.g., active material dissolution and plating). Because of the small,though finite possibility that an internal-cell short may form in one ormore cells during the life of a battery pack, which may lead toperformance degradation or hazardous operating conditions (e.g.,excessive heat generation, over-discharge, and the like.), it isimportant to identify the presence of cell shorts, particularly apresence of cell shorts during charging.

Typical battery cell packs used in electric vehicles (EVs) employ amultitude (e.g., thousands) of individual battery cells organized insub-units (sometimes referred to as modules or bricks) that areinterconnected. The cells and modules are combined variously in seriesand parallel to provide sustained high-energy storage and output asdesired for any particular application.

Obtaining and evaluating specific and accurate information regarding anindividual cell in this environment can be difficult. Data is evaluatedindividually and at a specific level but also takes into accountmacroscopic and gross level conditions of the application and batterypack to provide some context for the specific detailed information.

Accordingly, what is needed is an apparatus and method for identifyingthe presence of a short circuit in a battery pack.

BRIEF SUMMARY OF THE INVENTION

Disclosed is an apparatus and method for identifying a presence of ashort circuit in a collection of interconnected battery cells, thecollection including one or more cells used in one or more batterypacks. Preferably the collection includes a lithium-ion cell chemistry,or the like, and the collection used in electric-vehicle-battery packs.A fault-detection apparatus for a charging system that charges acollection of interconnected battery cells, the safety system includes adata-acquisition system for receiving a set of data parameters from thecollection while the charging system is actively charging thecollection; a monitoring system evaluating the set of data parameters toidentify a set of anomalous conditions; and a controller comparing theset of anomalous conditions against a set of predetermined profilesindicative of an internal short in one or more cells of the collection,the controller establishing an internal-short state for the collectionwhen the comparing has a predetermined relationship to the set ofpredetermined profiles.

A fault-detection method for a charging system that charges a collectionof interconnected battery cells, the method including a) receiving a setof data parameters from the collection while the charging system isactively charging the collection; b) evaluating the set of dataparameters to identify a set of anomalous conditions; c) comparing theset of anomalous conditions against a set of predetermined profilesindicative of an internal short in one or more cells of the collection;and d) establishing an internal-short state for the collection when thecomparing step identifies a predetermined relationship of the set ofdata parameters to the set of predetermined profiles.

The present invention provides several different systems and methodsthat may be used to identify when a cell is behaving abnormally and mayhave an internal-cell short. A further understanding of the nature andadvantages of the present invention may be realized by reference to theremaining portions of the specification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chart of a simplified multistage (4 stage) fast chargeprofile for a battery charger;

FIG. 2 is a representative charging system;

FIG. 3 is a chart of a first set of anomalous charge behavior responsiveto an internal short;

FIG. 4 is a chart of a second set of anomalous charge behaviorresponsive to an internal short;

FIG. 5 is a chart of a third set of anomalous charge behavior responsiveto an internal short;

FIG. 6 is a chart of a fourth set of anomalous charge behaviorresponsive to an internal short;

FIG. 7 is a chart of a fifth set of anomalous charge behavior responsiveto an internal short;

FIG. 8 is a chart of a sixth set of anomalous charge behavior responsiveto an internal short; and

FIG. 9 is a general flowchart of an internal-short detection processaccording to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention provide an apparatus and method foridentifying a presence of a short circuit in a battery pack. Thefollowing description is presented to enable one of ordinary skill inthe art to make and use the invention and is provided in the context ofa patent application and its requirements. Various modifications to thepreferred embodiment and the generic principles and features describedherein will be readily apparent to those skilled in the art. Thus, thepresent invention is not intended to be limited to the embodiment shownbut is to be accorded the widest scope consistent with the principlesand features described herein.

In the following text, the terms “energy-storage system,”“energy-storage assembly,” “battery,” “cell,” “brick,” “battery cell,”“battery-cell pack,” “pack,” “electrolytic-double-layer capacitor,” and“ultracapacitor” may be used interchangeably (unless the contextindicates otherwise) and may refer to any of a variety of differentrechargeable configurations and cell chemistries described hereinincluding, but not limited to, lithium ion (e.g., containing a lithiummetal oxide cathode and a graphite anode and the like), lithium-ionpolymer, nickel-metal hydride, nickel cadmium, nickel hydrogen, nickelzinc, silver zinc, or other chargeable high energy storagetype/configuration. A context for one implementation is use ofrechargeable Li-ion battery packs designed for plug-in electric vehicles(PHEV, HEY, and EV and the like), though other industrial applicationsfor such high-energy battery packs may implement variations to theinvention described herein without departing from the present invention.

FIG. 1 and FIG. 2 provide an exemplary implementation to provide one ofmany different contexts for the present invention to aid inunderstanding. FIG. 1 is a chart of a possible charge profile 100 for abattery charger applicable to various battery chemistries, mostpreferably to a battery including lithium ion/polymer cell chemistry andthe like. The preferred embodiment for charge profile 100 includes afirst stage “A,” typically followed by one or more other stages, showncollectively as “B” in FIG. 1. The various stages may include a constantcurrent (CC) stage, a constant voltage (CV) stage; a constant power (CP)stage, combinations of these, and the like.

A representative basic charge algorithm, though the invention is not solimited, includes charge at constant current (e.g., 0.2 C to 0.7 Cdepending on manufacturer, where C represents the current required toreach 100% capacity in one hour) until the battery reaches a desired VPC(volts per cell), for example 4.2 VPC, and hold the voltage at 4.2 voltsuntil the charge current has dropped to a predetermined portion (forexample −10%) of the initial charge rate. The termination condition isthe drop in charge current to a predetermined level. The top chargingvoltage, the termination current, number and type of charging stages,varies with the manufacturer. Embodiments of the present invention aregenerally applicable to any type of charge.

FIG. 2 is a representative embodiment for a charging system 200, such asmay be used in an electric vehicle and implement the present invention.The present invention is not limited to the specifics of theimplementation of the charging system or the nature of the application.System 200 includes a battery 205, a charger 210 coupled to battery 205and a battery management system (BMS) 215 and a battery data acquisitionand monitoring subsystem 220. A communication bus 225 couples subsystem220 to BMS 215 and a communication bus 230 couples BMS 215 to charger210. A communication bus 235 couples battery data from battery 205 tosubsystem 220.

Battery 205 is shown as a series-connected group of battery cells,however the arrangement of cells may be a combination of parallel/seriesconnected cells of many different arrangements. Charger 210 of thepreferred embodiment provides the charging current applied to battery205. BMS 215 controls the charging current according to a profileestablished by the embodiments of the present invention. Subsystem 220acquires the desired data as described herein regarding battery 205. Forexample, the data may include voltage, SOC, temperature, and otherapplicable data used by BMS 215. In some embodiments, subsystem 220 maybe part of BMS 215 and BMS 215 may be part of charger 210. One or moreof charger 210, BMS 215, and subsystem 220 control a switch 240.

In actual practice, combinations of constant-current (CC),constant-power (CP), and constant-voltage (CV) steps/phases are oftenused, though there are other charging profiles that could be used. Someof the disclosed apparatus and methods are dependent upon use of one ormore of these charging steps, or phases, while other apparatus andmethods are generically applicable to a wider range of chargingprofiles. Other, less standard, charging profiles may be adapted usingthe present invention to detect potential fault conditions with thespecifics of those implementations, without departing from the spiritand scope of the present invention.

During charging, the cell and brick voltage is expected to alwaysincrease, assuming an unchanging charge current, negligible load on thebattery, and taking into account expected variations in cell impedancedue to temperature and state-of-charge (SOC). When all of theseconditions are met, the change in cell and block voltage over timeshould always be greater than or equal to zero. A decrease in voltagemay indicate a decrease in the internal resistance of the cell and/orself-discharge. Similarly, during a constant voltage (CV) portion ofcharge, an increase in current would indicate a decrease in the internalresistance of the cell and/or self-discharge. Self-discharge of the cellabove a certain rate (determined through testing a large population ofcells without internal shorts) indicates that an internal-cell short ispresent.

Table I, below, summarizes several different methods that may be used toidentify when a cell is behaving abnormally and may have aninternal-cell short. Correspondingly, the battery-management system isable to measure many different properties, a set of data properties, toidentify the presence of such a short.

TABLE I Methods and Measurements for Determining the Presence of anInternal Short in a Battery Pack. # Data Properties Set AnomalousBehavior Indicating Possible Internal-Cell Short 1 Decreasing voltageduring A decreasing voltage (dV/dt < 0 or dV/dQ < 0 where Q is charge(CC, CV, or CP charge capacity) with charging current active (I_(charge)= true) and charging) charging current not decreasing in the case of CCor CP. This method could also measure an abnormally high dV/dQ when theshort is no longer active and the cell returns to its original voltagecurve (e.g., see FIG. 3). Note that with respect to decreasing voltage,this method monitors for false trips due, for example, to (i) stepchange from one CC level or CP level to another, (ii) reduction incharge rate due to grid power or charger power limits in the presence ofan HV AC load for example, (iii) external heating of the battery causinga reduction in impedance, or (iv) reduction in impedance at a rate whichcauses the loaded voltage to fall more quickly than the OCV rises. 2Increasing current to the An increase in charging current over time(dI/dt > 0 or dI/dQ > battery during the CV 0). portion of charge Notethat this method monitors for false trips in the case that the HV ACturns on at the beginning of CV and then turns off There may be othersimilar items that would need to be masked. 3 Abnormally large ratio ofCV_(time)/CC_(time) > (CVICC)_(max) or CV to CC or CV to CPCV_(time)/CP_(time) > (CVICP)_(max) charge time (where the max value isdetermined through testing and contained in a look-up table). Thismethod makes use of an extensive look-up table for charge from partialstate-of charge. This method takes into account shallow and full chargesas well as SOC inaccuracy as well as temperature. 4 Abnormally longcharge t_(charge) > t_(maxcharge) time for specified charge (where themax value is determined through testing and rate contained in a look-uptable) This method takes into account that charge power availability tothe battery is not necessarily constant 5 Enhanced rate of self-Self-discharge rate (average watts based on change in SOC over dischargetime when not charging or driving) > (SDR)_(max), or Bleed Ah > (BleedAh)_(max), or Bleed frequency or cumulative bleed Ah of one brick <<other bricks which indicates it is self discharging faster on its ownand does not need to be bled (where the max value is determined throughtesting and contained in a look-up table) (“Bleeding” is the process ofbalancing bricks to one another by discharging bricks with highervoltage.) 6 Low charge efficiency (ratio Charge efficiency < (CE)_(min)of discharge to charge (where the min value is determined throughtesting and capacity, Ah/Ah) contained in a look-up table). This methoduses an extensive look-up table for charge from partial state of charge,variable temperature, and the like. 7 Charge Ah compared to Charge Ah I[(Charge Start SOC − Charge End SOC)* Ah] > 1.X expected charge Ah Thismethod detects if more charge is passed than is theoretically possiblefrom the initial SOC. 8 SOC and temperature Measured Brick impedance((CCV − OCV (for specific SOC) I compensated impedance charge current)<< look up table based on SOC and temperature drop. or A real timeimpedance Change in measured Brick impedance ((CCV − OCV (formeasurement (R,) is made specific SOV) I charge current) reduces fasterthan max rate by the battery firmware (based on normal rates of changeof temperature and SOC during charge. An impedance measurement will bemade that is below the threshold for unhealthy cells with activeinternal shorts. 9 Temperature of cell, brick, Measure temperatureincrease for a cell in a parallel brick of or cooling medium is cells,temperature increase in the effluent of the cooling medium greater thanthreshold value. above T max Measure the temperature difference betweenthe inlet and outlet of the cooling medium. Normal (no internal short)charge will result in a predictable difference between the inlet andoutlet temperature. An internal short during charge will result in adifferential that is greater than prediction. An algorithm can bedeveloped that predicts the differential based on charge rate, initialSOC at charge, initial ESS temp, ambient temperature and charge time.

Each of the above methods represents a different way to detect apotential internal-cell short by evaluating data derived from thebattery pack for anomalous conditions, including an anomalous change incell impedance over time, an anomalous increase in total charge passed,or an anomalous change in temperature, all of which may be indicative ofinternal-cell shorts in the proper context. Pack electronics may beengineered to monitor necessary parameters, for example, brickimpedance, for anomalies. This monitoring, depending uponimplementation, preferably includes frequent/continuousacquisition/measurement/evaluation of the relevant data set. Some of theconditions are subtle and appropriate evaluation of the particularcontext (e.g., driving, charging, parking, and the like) is important indetermining the proper conclusion to be drawn from the data.

In an exemplary embodiment, when any of the conditions noted in Table Iare true, an internal-short flag state is set indicative of a potentialunsafe condition. This is not to say that a particular applicationrequires all methods to be implemented or that an application may nothave additional or different methods employed. It may be the case that asingle methodology is sufficient for the particular application.

Depending upon a particular implementation, there may be differentresponses to the setting of this flag state. For example, charging canbe terminated (with further charging inhibited) and a self-dischargetest can be run automatically as a diagnostic. The operator of thevehicle could be notified that they will be unable to recharge thevehicle until it is brought to a service station for evaluation. At thatpoint, the results from the self-discharge test could be evaluated and asimple charge/discharge test run to determine whether the pack is in apotentially unsafe operating condition.

Additional features and characteristics of the disclosed methods areseen from a review of the following figures: FIG. 3 through FIG. 9. FIG.3 provides an example of decreasing voltage during the constant-currentor constant-power portion of charge (solid lines depict normal chargeconditions; dashed lines indicate a representative occurrence if aninternal short formed at that point during charge-because some charge isdissipated through an internal short, the charge will be extended). FIG.4 provides an example of an increasing current during CV portion ofcharge and an increase in total charge current passed (solid linesdepict typical charge behavior—increasing voltage during theconstant-current portion of charge and constant voltage with decreasingcurrent during the constant-voltage portion of charge; dashed linesdepict an anomaly in the charge behavior caused by an internal-cellshort. The total charge current passed increases as some of the currentis dissipated through the internal short). FIG. 5 provides test resultsfrom a battery showing a decrease in voltage during a CC portion ofcharge where the current to the battery is unchanging (note that in thecase that the current drops a bit during CP or CC due to some othercomponent taking power from the charger, a drop would be expected). FIG.6 provides test results from a battery showing an increase in currentduring the CV portion of charge. FIG. 7 provides test results from abattery showing an increase in current during the CV portion of charge.FIG. 8 provides test results from a battery showing an increase incurrent during the CV portion of charge with a coincident increase inthe battery temperature (temperature spikes due to internal-cell shortsare undesirable and may lead to hazardous conditions). FIG. 9 is ageneral flowchart of an internal-short detection process according to anembodiment of the present invention. In FIG. 3 through FIG. 8, theprofiles and magnitudes of the values are representative and actual dataparameters in an operating system will vary from those shown and thethresholds/conditions indicative of the described methods areappropriately adapted for the particularities of each application andimplementation.

In FIG. 9, a preferred process of the present invention detectsanomalous conditions possibly associated with an internal-short in oneor more cells of battery (as shown, for example, anomalous conditionsassociated with impedance, passed charge, and cell/battery temperature),evaluating the conditions to establish that an internal-short does, oris likely to exist (probability exceeding some predetermined thresholdfor example) to set an internal-short flag. In some embodiments, thatwill be the extent of the process as some other system or process willrespond to the setting of the internal-short flag. In the preferredembodiment, charge behavior is modified responsive to the setting of theinternal-short flag. For example, modifying charge behavior includesmany different types of operation, from suspending/inhibiting charging,limiting charging in some fashion (e.g., charging to an SOC less than100% or use slower charge rate and the like), initiating strictertemperature limits/checks inside the cell, and the like.

Methods 1 and 2 above (i.e., decreasing voltage during charge andincreasing current during CV charge) can be measured during any chargecycle that begins with V<V_(max) and deltaT<(deltaT)_(max), where deltaTis the maximum difference in temperature between the cells throughoutthe battery pack and the ambient temperature and (deltaT)_(max) is themaximum acceptable difference in temperature that would affect a changein voltage or current during charging, this value being determinedthrough testing and contained in a look-up table. The battery-managementsystem verifies that the charge current has not decreased or beeninterrupted, and that no additional loads have been introduced (i.e.,HVAC) before indicating a hazardous condition.

Methods 3 through 7 use time or capacity measurement. For methods 3 and4, a time counter can be used to determine if the battery has beencharging longer than the time indicated in a look-up table for a pack ofthat capacity and state of charge. This look-up table may be compiledfrom pack data, as well as from resistance measurements and cycling datafrom cells at end-of life. These measurements also require thatdeltaT<(deltaT)_(max). For method 5, the self-discharge rate of the packcan be measured and compared with the self-discharge rate for a cell ofthat capacity without an internal-cell short present (from a look-uptable). This can be measured using voltage measurements over time, or,if a bleed circuit is present, it can be measured by determining theamount of Ah passed through the bleed circuit to balance the seriesblocks of cells. These methods take into consideration shallow and fullcharges, as well as SOC inaccuracy.

Method 6 (charge efficiency) is similar to method 5 in that it measuresthe amount of self-discharge. This method also requires that anytemperature, rate, and cutoff voltage differences between charge anddischarge are accounted for. If an internal-cell short is present, thecharge capacity will increase (some current is going through the short)and if the short is maintained the discharge capacity will decreaserelative to a cell without a short. The ratio of the discharge to thecharge capacity should be 1 for a fully reversible cell without shortsor side reactions. This value is typically ˜99.97 or higher for newcells without shorts. For a cell with an internal short, this value maybe ˜70% or lower. A low-end limit value is determined through testingfor the cell in use and this value will be included in a look-up tablefor the battery management system.

Method 7 may be the most simple to implement for some applications,especially in a large battery pack such as the type of pack that mightbe used in an electric vehicle. This method measures the total chargepassed to the pack, module, or parallel brick. If the total chargepassed exceeds the expected charge capacity from the initial to finalstate of charge (SOC), then the additional charge may have beendissipated through internal shorts. In a vehicle battery, the capacityis continuously monitored in order to estimate remaining range. Thecalculated Ah capacity (CAC) is monitored as the pack ages, enablingthis method to be used throughout the life of the battery pack. Say forexample that a 100 Ah battery pack is assembled and it is at 20% SOCinitially, or 20 Ah of energy is available in the pack. This examplepack contains cells with internal shorts and takes 130 Ah (an additional110 Ah) to reach full pack voltage. This means that 30 Ah weredissipated through internal cell shorts and caused the pack to heat up,potentially creating a hazardous condition. By comparing the totalcharge passed to the expected value, this method may be used tointerrupt charge, potentially before a hazardous condition can occur.Method 7 is doubly useful in that it can also be used as another layerof protection against pack overcharge, a highly hazardous conditionshould it occur.

Method 8 involves a real-time measurement of the impedance of parallelbricks of cells, and potentially also series strings of cells. Thismeasurement is continuously made during pack operation to estimateavailable power using a combination of voltage and current measurements.During charge, these measurements are typically not made. However, someembodiments of this invention propose use of a continuous estimation ofbattery impedance to detect an internal short. For a given SOC, theexpected impedance can be kept in a look-up table. If the impedance atthat SOC is lower than the threshold value, it may indicate that aninternal cell short has formed. This would capture the case of adecreasing voltage during CC or CP charge as well as an increase incurrent during CV charge. As indicated above, any additional load on thebattery pack or change in temperature is properly accounted for.

Method 9 involves the direct measurement of a resultant increase intemperature due to an internal-cell short. The cell, brick, and coolanttemperature (refrigerant, water, air or another working fluid) ismonitored continuously. If it increases in temperature more rapidlyand/or to a higher value than is expected for that charge condition, ahazardous condition is indicated and the charge is interrupted.

Due to the higher number of cells that are used in parallel in ahigh-energy pack such as those used in an electric vehicle, sensitivebattery electronics are necessary in order to detect a decrease involtage on charge, an increase in current on CV charge, an enhancedself-discharge rate, the temperature distribution throughout the batterypack, the charge time, and accurate charge and discharge capacity. Thesebattery electronics are quite sophisticated and require a finite currentdraw. This current draw is accounted for in choosing the limits for thelook-up table.

To avoid an imbalance in the voltage of blocks of cells in series, ableed circuit may be used to match block voltages. This bleed circuitcan be used to identify a block of cells with an enhanced rate ofself-discharge (bleed Ah or frequency of bleeding).

Using method 7 requires some sensitivity in measuring the chargecapacity to a brick. Cells with a current bump might have an increase incharge capacity of more than a factor of 2 (half of the total charge Ahpassed are dissipated through an internal short, creating heat). For aparallel brick with 22 cells, this means that the pack electronicspick-up on an increase of brick capacity. Table II summarizes therequired sensitivity, assuming a factor of 2 increase in charge Ahpassed.

TABLE II Number of cells Percent increase with current in charge bumpcurrent in brick 1 4.55 2 9.09 3 13.64 4 18.18 5 22.73 6 27.27 7 31.82 836.36 9 40.91 10 45.45 11 50 12 54.55 13 59.09 14 63.64 15 68.18 1672.73 17 77.27 18 81.82 19 86.36 20 90.91 21 95.45 22 100.00

The system above has been described in the preferred embodiment of anembedded automobile (EV) electric charging system for lithium ion andrelated cell chemistries. Other applications and cell chemistries arecontemplated to be within the scope of the present invention, including,for example, NiMH collections. For example, NiMH cells charge until thevoltage decreases (due to side reactions in the cell). In such cellchemistries, an anomalous decrease in voltage (e.g., a magnitude of theactual voltage decrease exceeding a predetermined thresholdSOC_(decrease) value) may indicate internal shorting.

The system, method, and computer program product described in thisapplication may, of course, be embodied in hardware; e.g., within orcoupled to a Central Processing Unit (“CPU”), microprocessor,microcontroller, System on Chip (“SOC”), or any other programmabledevice. Additionally, the system, method, and computer program product,may be embodied in software (e.g., computer readable code, program code,instructions and/or data disposed in any form, such as source, object ormachine language) disposed, for example, in a computer usable (e.g.,readable) medium configured to store the software. Such software enablesthe function, fabrication, modeling, simulation, description and/ortesting of the apparatus and processes described herein. For example,this can be accomplished through the use of general programminglanguages (e.g., C, C++), GDSII databases, hardware descriptionlanguages (HDL) including Verilog HDL, VHDL, AHDL (Altera HDL) and soon, or other available programs, databases, nanoprocessing, and/orcircuit (i.e., schematic) capture tools. Such software can be disposedin any known computer usable medium including semiconductor (Flash, orEEPROM, ROM), magnetic disk, optical disc (e.g., CDROM, DVD-ROM, etc.)and as a computer data signal embodied in a computer usable (e.g.,readable) transmission medium (e.g., carrier wave or any other mediumincluding digital, optical, or analog-based medium). As such, thesoftware can be transmitted over communication networks including theInternet and intranets. A system, method, computer program product, andpropagated signal embodied in software may be included in asemiconductor intellectual property core (e.g., embodied in HDL) andtransformed to hardware in the production of integrated circuits.Additionally, a system, method, computer program product, and propagatedsignal as described herein may be embodied as a combination of hardwareand software.

One of the preferred implementations of the present invention is as aroutine in an operating system made up of programming steps orinstructions resident in a memory of a computing system as well known,during computer operations. Until required by the computer system, theprogram instructions may be stored in another readable medium, e.g. in adisk drive, or in a removable memory, such as an optical disk for use ina CD ROM computer input or other portable memory system for use intransferring the programming steps into an embedded memory used in thecharger. Further, the program instructions may be stored in the memoryof another computer prior to use in the system of the present inventionand transmitted over a LAN or a WAN, such as the Internet, when requiredby the user of the present invention. One skilled in the art shouldappreciate that the processes controlling the present invention arecapable of being distributed in the form of computer readable media in avariety of forms.

Any suitable programming language can be used to implement the routinesof the present invention including C, C++, Java, assembly language, etc.Different programming techniques can be employed such as procedural orobject oriented. The routines can execute on a single processing deviceor multiple processors. Although the steps, operations or computationsmay be presented in a specific order, this order may be changed indifferent embodiments. In some embodiments, multiple steps shown assequential in this specification can be performed at the same time. Thesequence of operations described herein can be interrupted, suspended,or otherwise controlled by another process, such as an operating system,kernel, and the like. The routines can operate in an operating systemenvironment or as stand-alone routines occupying all, or a substantialpart, of the system processing.

In the description herein, numerous specific details are provided, suchas examples of components and/or methods, to provide a thoroughunderstanding of embodiments of the present invention. One skilled inthe relevant art will recognize, however, that an embodiment of theinvention can be practiced without one or more of the specific details,or with other apparatus, systems, assemblies, methods, components,materials, parts, and/or the like. In other instances, well-knownstructures, materials, or operations are not specifically shown ordescribed in detail to avoid obscuring aspects of embodiments of thepresent invention.

A “computer-readable medium” for purposes of embodiments of the presentinvention may be any medium that can contain, store, communicate,propagate, or transport the program for use by or in connection with theinstruction execution system, apparatus, system or device. The computerreadable medium can be, by way of example only but not by limitation, anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus, system, device, propagation medium, orcomputer memory.

A “processor” or “process” includes any human, hardware and/or softwaresystem, mechanism or component that processes data, signals or otherinformation. A processor can include a system with a general-purposecentral processing unit, multiple processing units, dedicated circuitryfor achieving functionality, or other systems. Processing need not belimited to a geographic location, or have temporal limitations. Forexample, a processor can perform its functions in “real time,”“offline,” in a “batch mode,” etc. Portions of processing can beperformed at different times and at different locations, by different(or the same) processing systems.

Reference throughout this specification to “one embodiment”, “anembodiment”, or “a specific embodiment” means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention and notnecessarily in all embodiments. Thus, respective appearances of thephrases “in one embodiment”, “in an embodiment”, or “in a specificembodiment” in various places throughout this specification are notnecessarily referring to the same embodiment. Furthermore, theparticular features, structures, or characteristics of any specificembodiment of the present invention may be combined in any suitablemanner with one or more other embodiments. It is to be understood thatother variations and modifications of the embodiments of the presentinvention described and illustrated herein are possible in light of theteachings herein and are to be considered as part of the spirit andscope of the present invention.

Embodiments of the invention may be implemented by using a programmedgeneral purpose digital computer, by using application specificintegrated circuits, programmable logic devices, field programmable gatearrays, optical, chemical, biological, quantum or nanoengineeredsystems, components and mechanisms may be used. In general, thefunctions of the present invention can be achieved by any means as isknown in the art. Distributed, or networked systems, components andcircuits can be used. Communication, or transfer, of data may be wired,wireless, or by any other means.

It will also be appreciated that one or more of the elements depicted inthe drawings/figures can also be implemented in a more separated orintegrated manner, or even removed or rendered as inoperable in certaincases, as is useful in accordance with a particular application. It isalso within the spirit and scope of the present invention to implement aprogram or code that can be stored in a machine-readable medium topermit a computer to perform any of the methods described above.

Additionally, any signal arrows in the drawings/Figures should beconsidered only as exemplary, and not limiting, unless otherwisespecifically noted. Furthermore, the term “or” as used herein isgenerally intended to mean “and/or” unless otherwise indicated.Combinations of components or steps will also be considered as beingnoted, where terminology is foreseen as rendering the ability toseparate or combine is unclear.

As used in the description herein and throughout the claims that follow,“a”, “an”, and “the” includes plural references unless the contextclearly dictates otherwise. Also, as used in the description herein andthroughout the claims that follow, the meaning of “in” includes “in” and“on” unless the context clearly dictates otherwise.

The foregoing description of illustrated embodiments of the presentinvention, including what is described in the Abstract, is not intendedto be exhaustive or to limit the invention to the precise formsdisclosed herein. While specific embodiments of, and examples for, theinvention are described herein for illustrative purposes only, variousequivalent modifications are possible within the spirit and scope of thepresent invention, as those skilled in the relevant art will recognizeand appreciate. As indicated, these modifications may be made to thepresent invention in light of the foregoing description of illustratedembodiments of the present invention and are to be included within thespirit and scope of the present invention.

Thus, while the present invention has been described herein withreference to particular embodiments thereof, a latitude of modification,various changes and substitutions are intended in the foregoingdisclosures, and it will be appreciated that in some instances somefeatures of embodiments of the invention will be employed without acorresponding use of other features without departing from the scope andspirit of the invention as set forth. Therefore, many modifications maybe made to adapt a particular situation or material to the essentialscope and spirit of the present invention. It is intended that theinvention not be limited to the particular terms used in followingclaims and/or to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include any and all embodiments and equivalents falling within thescope of the appended claims. Thus, the scope of the invention is to bedetermined solely by the appended claims.

What is claimed is:
 1. A fault-detection apparatus for a charging systemthat charges a collection of interconnected battery cells, the apparatuscomprising: a) a data-acquisition system for receiving a set of dataparameters from the collection while the charging system is activelycharging the collection, the set of data parameters measured during acharge cycle that begins with V<V_(max) and deltaT<(deltaT)_(max),wherein deltaT is a maximum difference in temperature between the cellsthroughout the collection and an ambient temperature, wherein(deltaT)_(max) is a maximum acceptable difference in temperature thataffects a change in voltage or current during charging; b) a monitoringsystem evaluating said set of data parameters to identify a set ofanomalous conditions; and c) a controller comparing said set ofanomalous conditions against a set of predetermined profiles indicativeof an internal short in one or more cells of the collection, saidcontroller establishing an internal-short state for the collection whensaid comparing has a predetermined relationship to said set ofpredetermined profiles.